Programmers use Null as different flags. It can hint an absence, an undefined value, en error etc.
Multiple semantics lead to coupling and errors.

TL;DR: Null is schizofrenic and does not exist in real world. His creator regreted and programmers around the world suffer it. Don't be a part of it.

Problems

• Coupling among the callers and the senders.

• Mismatch among the callers and the senders.

• If/Switch/Case Polluting.

• Null is not polymorphic with real objects. Hence, Null Pointer Exception

• Null does not exist on real world. Thus, it violates Bijection Principle

Solutions

• Avoid Null. 

• Use NullObject pattern to avoid ifs.

• Use Optionals.

Null: The Billion dollar mistake

Maxi Contieri ・ Nov 18 '20

#codenewbie #tutorial #programming #webdev

Exceptions

• APIs, Databases and external systems where NULL does exist.

Sample Code

Wrong

class CartItem{
  constructor(price) {
     this.price = price;
  }
}

class DiscountCoupon {
  constructor(rate){
    this.rate = rate;
  } 
}

class Cart{        
    constructor(selecteditems, discountCoupon){
        this.items = selecteditems;
        this.discountCoupon = discountCoupon;
    }     
    subtotal(){    
        return this.items.reduce